Piroxicam is a compound called by a chemical name of 4-hydroxy-2-methyl-N-(2-pyridyl)-2H-1,2-benzothiazine-3-carboxamide-1,1-di oxide and has an excellent antiphlogistic and analgesic effect. It has hence been widely used clinically at present.
Piroxicam is mostly prepared in the form of an oral preparation and in the forms of a suppository and an ointment in extreme part.
However, the oral preparation has involved a problem of side effects such as a disorder of the digestive tract. Although the side effects are somewhat reduced by the suppository compared with the oral preparation, the disorder of the digestive tract has been still recognized on the suppository. Moreover, these preparations have been difficult to effectively deliver their active ingredients to the diseased area. The ointment by which piroxicam can be topically applied has been proposed in order to remedy the above drawbacks involved in the oral preparation and suppository. However, this preparation has also been accompanied by drawbacks that its dose is inaccurate and its base ingredients adhere to clothes to smear them.
A plaster is the most effective form for percutaneously administering the drug to deliver it to the diseased area Japanese Patent Application Laid-Open No 316314/1989 discloses that a plaster in which lornoxicam, tenoxicam, piroxicam or sulindac is incorporated exhibit higher antiphlogistic and analgesic effect compared with a plaster in which a non-steroidal antiphlogistic-analgesic drug such as indomethacin, diclofenac, flurbiprofen or ketoprofen is incorporated. However, its effect is insufficient and it also offers a problem of physical properties as a plaster. Therefore, it is unfit for use and hence not yet provided in the clinical field under circumstances.
As described above, a satisfactory effect has not been successfully achieved even when piroxicam has been incorporated into a base for a plaster because its percutaneous absorption is poor.
Therefore, it is an object of the present invention to provide a piroxicam-containing plaster excellent in percutaneous absorption of piroxicam.
In view of the foregoing circumstances, the present inventors have carried out an extensive investigation. As a result, it has been found that triacetin and triethyl citrate have an effect of facilitating the percutaneous absorption of piroxicam, thus leading to completion of the present invention.